Many people use mobile stations, such as cell phones and personal digital assistants (PDAs), to communicate with cellular wireless networks. These mobile stations and networks typically communicate with each other over a radio frequency (RF) air interface according to a wireless communication protocol such as Code Division Multiple Access (CDMA), perhaps in conformance with one or more industry specifications such as IS-95, IS-2000, or IS-856. Wireless networks that operate according to these specifications are often referred to as access networks. These access networks typically provide communication services such as voice, Short Message Service (SMS) messaging, and packet-data connectivity.
A mobile station operating in an access network is typically referred to as a wireless access terminal (or simply an “access terminal”), while the network entity with which the wireless access terminal communicates over the air interface is known as a wireless access node (or simply an “access node”). The wireless access node typically includes a device known as a radio network controller (RNC) or base station controller (BSC). The wireless access node may also include one or more base stations (also known as base transceiver stations (BTSs)), each of which includes one or more antennas that radiate to define respective wireless coverage areas within the larger coverage area served by the access network. Among other functions, the RNC controls one or more base stations, and acts as a conduit between the base stations and an entity known as a packet data serving node (PDSN), which provides access to a packet-data network. Thus, when positioned in one of these wireless coverage areas, a wireless access terminal may communicate over the packet-data network via the wireless access node and the PDSN.
Many service providers currently use wireless networks that provide service under a protocol known as EV-DO, which stands for “Evolution Data Optimized.” EV-DO networks, operating in conformance with industry specification EV-DO, provide high rate packet-data service (including Voice over IP (VoIP) service) to mobile stations using a combination of time-division multiplexing (TDM) on the forward link (from the network to mobile stations) and CDMA technology on the reverse link (from mobile stations to the network).
When congestion occurs on the reverse-link, an access node may employ a reverse-activity bit (RAB) to control or adjust the load on the reverse-link. More specifically, in each timeslot, an EV-DO access node typically transmits an RAB to all the access terminals operating in the sector it serves. The RAB indicates either that the access terminal may continue its communications on the reverse-link with no change, or that the access terminal should adjust its reverse-link activity.